During bypass operations on cable lines, a bypass cable and related devices are often used to quickly build a bypass power supply line in the field, bridging a to-be-inspected or to-be-rush-repaired cable line segment or device, where reverse switching is used to substitute the original line with the bypass line for providing power supply to users. In the meantime, workers perform maintenance, overhaul and replacement operations on the to-be-inspected cable line segment or device in the original line at power off state. In bypass operations for inspecting and repairing a ring main unit, there are two main difficulties when building the bypass cable system. First, a power supply point should be connected, which is generally a spare section of a nearby ring main unit; second, environment for laying the bypass cable should be good, avoiding frequent road crossing. The two difficulties and load-intensive characteristics of city center area contradicts each other, because ring main units in city center area rarely have a spare section. In the search for a power supply point, further locations are searched to find another ring main unit having the spare section, which extends the distance for laying bypass cable line, increases the amount of construction work, prolongs operation period, increases the quantity of bypass devices, and thus raising security risks.
Based on practical needs of field operations, if there could be a switching equipment developed to connect an incoming cable of the original ring main unit with a bypass cable, readily-laid power cable can become part of the bypass cable, solving the difficulties of power supply point and long-distance layout. 10 kV lines in domestic distribution network often adopt XLPE insulated power cables, an indoor cable terminal having naked wire-connecting terminal or a T-shaped cable terminal having closed line-connecting terminal is normally installed based on structures of the ring main unit, the connection mode between the indoor cable terminal and the ring main unit being bolt fastening mode. Bypass cable operation devices adopt flexible power cables, in the end of which are installed with quick connect and disconnect bypass cable connector. Cable junction box is a device often used in power lines for performing branching and transferring on cables. However, connectional cable junction box is limited by its structure and cannot be directly connected to a bypass cable.